International Patent Publication No. WO 2005/066488 A1, for example, describes a device for ignition of an internal combustion engine, which device includes an ignition laser. The ignition laser has at the end thereof toward the combustion chamber a combustion chamber window which is transmissive for the laser pulses emitted by the ignition laser. At the same time, the combustion chamber window must withstand the high pressures and temperatures prevailing in the combustion chamber and must seal off the interior of the ignition laser from the combustion chamber. In that situation, high surface temperatures and pressures, and also soiling, for example in the form of oil ash deposits, particles, etc., may occur especially at the surface of the combustion chamber window facing the combustion chamber.
In the case of the known device, it is to be regarded as a disadvantage that certain constituents of exhaust gases, for example oil ashes or soot, damage the combustion chamber window, for example by being deposited on the combustion chamber window and impairing its properties, in particular transmission for laser radiation.